High current relatively low voltage power transmission from transformers or generators to using apparatus such as welders or motors frequently employs bus bars which usually extend through enclosures and through enclosed panels where branches or connections are made. Most such power transmission is a three phase system or a three phase and neutral system. Each phase and the neutral are laterally spaced. The spacing between phases and the neutral may be from about 50 to about 90 mm. If each phase is a multi-bar system or more than a single bar, such as three bars, then the phase spacing is usually measured from the center bar thus reducing the open spacing between phases. In a multi-bar phase, the spacing between bars within a phase is much less. For copper bars, the lateral spacing between bars in a given phase may run from about 4 to about 15 mm, depending on a number of factors such as bar size. A typical lateral spacing dimension within a phase would be on the order of 5 mm.
In the construction of such systems, safety panel enclosures are required and sometimes the multi-bar three phase system has to be constructed in the panel enclosure, although it is more convenient to construct the enclosure after the system is assembled. However, if the system needs to be modified or adjusted after assembly, connections will need to be installed or removed within the enclosure. Such enclosures usually have front access doors, but fixed back, side and top walls. They present cramped quarters, may not be well lighted, and make it extremely difficult to create or remove connections such as shunts, lugs, or bars. The problem is complicated not only by the space requirements, but also by the type of connection which has to be made. High contact pressure is necessary to obtain a good electrical connection and yet concentrated pressure can cause deformation of the bus bar which can cause loosening of the connection. Also, care must be taken that there is not an excess of steel against the bus bar which can lead to unwanted heat rise. Too much steel leads to magnetic conditions which causes heat rise. Excess heat may also cause condensation and corrosion.
Conventional fastening systems utilize nut and headed bolts with flat washers. While the fastening to bus bars is much easier with perforated bus bar having edge holes at predetermined edge and length spacing, such as sold by ERICO FRANCE of Andrezieux-Boutheon, France under the trademark ERIFLEX.RTM., the tight spacing and cramped quarters nonetheless creates many problems. In order to make the proper connection or alteration, it is sometimes necessary to disassemble the system or the enclosure or both.
Since a headed bolt cannot be inserted in the space between bars of the same phase because of the close spacing (5 mm e.g.), it has to be inserted through all three bars of a three bar phase. If the connection is made between two of the three bars, a spacer is required between the two bars and the third. Two spacers may be required if the connection is made to the outside of an outside bar since the fastener has to go through all three bars. At the least, the fastening system requires a bolt, nut, four washers and one or two spacers, as well as two wrenches, one of which may be a torque wrench.
For a four bar phase, the problems and ports are multiplied. For unperforated bar, the installer must also drill precisely aligned holes through the bars and spacers and make sure that the clamped or stacked surfaces are burr, oxide, and grease free.
In such panel systems, the enclosure should remain clean and free of debris. Lost or dropped parts, which occur frequently, should be found and removed. Needless to say, retrieval of lost or dropped parts, or disassembly of the cabinet or panel bus bar system is time consuming. The making and fitting of spacers also adds to the cost. It would, accordingly, be desirable to have a bus bar fastening system which could be used in tight quarters and which could be installed quickly and conveniently from the front or open side of the panel cabinet without requiring so many parts and tools, and which would meet all of the pressure and other requirements to make a high quality electrical connection.